Recrystallization Kinetics in 17Cr 1Mo Ferritic Steel

摘要

The recrystallization kinetic of 17Cr IMo ferritic steel was studied using 60% cold rolled samples. The recrystallization was carried out at 750 , 800 and 900°C for 3, 5, 15, 30 and 60 minuets. The volume fraction of the recrystallized grains was used as a kinetic parameter. The magnitude of time exponent "n" was much less than the ideal value because of the heterogeneous recrystallization, The estimated activation energy for recrystallization "Q" was more as compared to those for pure metals Introduction Ferritic steels containing Cr of various level with 1-2 wt% Mo are known for their improved mechanical properties and superior corrosion resistance comparable to that of 316 austenitic stainless steel [1] They are also resistant to stress corrosion cracking Similarly, the low nickel content in these steels provides good resistance in sulphur-containing environment at high temperature [2], Hence, they are recommended for chemical, petrochemical, power generation and nuclear technology applications In this family "SR" trademark steel, containing higher Cr (6-24 wt%) with 18SR "Scale Resistance" series is found capable of resisting 100 hour exposure up to 1200°C [3] Moreover, 17Cr IMo composition which represents a very narrow range in Schaeffer diagram is widely recommended for automobile components like exhaust systems by virtue of its excellent corrosion resistance [3], Hence, very good fbrmability of these steels like rolling, deep-drawing are important for above applications. Since, these cold working processes introduce large defect concentration (highly strained) and make the steel susceptible to quick failure either by mechanical or chemical/corrosion process, it becomes necessary to recrystallize-anneal.